This paper has focused on estimating the marginal or unconditional distributions of X, Y, and D. Other types of analysis are also of interest, for example, the association of predictors, such as body mass index and smoking status, with X, D, or Y. Web Appendix 1 gives code for doing such an analysis, while accounting for left truncation or left censoring in the single-milestone case.
Cain, K., Harlow, S., Little, R., Nan, B., Yosef, M., Taffe, J., & Elliott, M. R. (2011). Bias due to left truncation and left censoring in longitudinal studies of developmental and disease processes. American Journal of Epidemiology, 173(9), 1078 - 1084. https://doi.org/10.1093/aje/kwq481